In recent years, there has been an active trend of digitalization of broadcasting, and fusion with communications has also progressed. In the field of communications, satellite digital broadcasting has already been started, and it is expected that terrestrial broadcasting will also be digitalized in the future.
As a result of digitalization of broadcast content, data broadcasting is also performed in addition to conventional video and audio. Also, in the communications field, digital content distribution via the Internet has begun with music, and Internet broadcasting stations that broadcast video have also appeared.
Henceforth, it is envisaged that continuous content media such as video and audio will enter the borne via various paths (transmission media). Through such fusion and digitalization of communications and broadcasting, it has become possible to offer previously unavailable services by means of metadata that describes content or relates to content.
For example, EPG information as well as audio/video information is provided by interleaving EPG (Electric Program Guide)—“Standard specification for program arrangement information used in digital broadcasting ARIB STD-B10 Version 1.1” or “pr ETS 300 468 Digital Broadcasting systems for television, sound and data services—Specification for Service Information (SI) in Digital Video Broadcasting (DVB) systems”) used in CS digital broadcasting, in an audio/video PES (Packetized Elementary Stream) using an MPEG-2 (Motion Picture coding Experts Group phase 2—“ISO/IEC 13818-1 to 3”) private section.
Also, in BS digital broadcasting, data broadcasting using MPEG-2 private PES packets is anticipated. Moreover, it is also possible to perform content management by inserting metadata that describes content in the format of user data in material transmission (“ANSI/SMPTE291M-1996 Ancillary Data Packet and Space Formatting”).
A conventional information processing system will be described below using FIG. 15. FIG. 15 is a block diagram of a conventional information processing system.
An information provision node 1501 is provided with a storage section 1502 in which an AV stream and metadata for describing the AV stream are stored. Also provided in the information provision node 1501 is an information provision section 1504 that multiplexes the AV stream and metadata stored in the storage section 1502 and generates and outputs a multiplex stream 1503. The information provision section 1504 transmits the multiplex stream 1503 to an information usage node 1506 via a network 1505.
Meanwhile, the information usage node 1506 is provided with an information usage section 1507 that extracts an AV stream and metadata from a multiplex stream and executes processing on them in order to use them. The information usage node 1506 is also provided with a storage section 1508 that stores the AV stream and metadata extracted by the information usage section 1507. The information usage section 1507 reads the AV stream and metadata stored in the storage section 1508 in order to use them.
Next, the information provision section 1504 will be described using FIG. 16. FIG. 16 is a block diagram of a conventional information provision section.
The information provision section 1504 is provided with an access section 1601 that reads an AV stream and metadata from the storage sect ion 1502. The access section 1601 outputs an AV stream 1602 and metadata 1603 to a multiplexing section 1604.
The multiplexing section 1604 transmits to the information usage node 1506 a multiplex stream 1503 that multiplexes the AV stream 1602 and metadata 1603.
Next, multiplex stream generation processing by the multiplexing section 1604 will be described using FIG. 17.
The drawing indicated by reference numeral 1503 in the drawing shows the MPEG-2 TS (Transport Stream) PES packet layer, and shows a multiplex stream. The drawing indicated by reference numeral 1702 shows a video PES packet, the drawing indicated by reference numeral 1703 shows an audio PES packet, and the drawing indicated by reference numeral 1703 shows a private PES packet. 1603 indicates the metadata PES packet layer, in which 1704 is a first PES packet comprising metadata and 1705 is a second PES packet comprising metadata.
The multiplexing section 1604 divides the metadata 1603 to make private PES packets, inserts the first PES packet 1704 and second PES packet 1705 in order as appropriate between AV streams consisting of video PES packets 1701 and audio PES packets 1702, and obtains a multiplex stream 1503 that is an MPEG-2 TS.
As conventional metadata is AV stream ancillary data—for example, small amounts of data such as titles—processing has been performed with metadata alone. That is to say, it has not been necessary to provide time synchronization of metadata with an AV stream. Therefore, since conventional metadata does not have a configuration that provides for synchronization with an AV stream, metadata has been packetized using virtually the same size, and has been inserted as appropriate between AV streams at virtually equal intervals.
The multiplexing section 1604 then sends this multiplex stream 1503 to the information usage node 1506.
Next, the information usage section 1507 will be described using FIG. 18. FIG. 18 is a block diagram of a conventional information usage section.
The information usage section 1507 is provided with an extraction section 1803 that performs separation and extraction, and output, of an AV stream 1801 and metadata 1802. The extraction section 1803 outputs the separated and extracted AV stream 1801 and metadata 1802 to an access section 1804.
The access section 1804 stores the AV stream 1801 and metadata 1802 input from the extraction section 1803 in a storage section 1508. Also, the access section 1804 outputs the AV stream 1805 and metadata 1806 read from the storage section 1508 to a display section 1807. The display section 1807 displays either or both of the AV stream 1805 and metadata 1806 input from the access section 1804.
Next, the processing of the information usage section 1507 will be described using FIG. 19. FIG. 19 is a processing flowchart of a conventional information usage section.
The extraction section 1803 performs metadata parsing—that is, syntax analysis (ST1901). Then, execution of the processing of the access section 1804 and display section 1807 is performed (ST1902).
In this way, a conventional information processing system can display a description relating to AV information, in addition to AV information, by means of the information usage node 1506 by having the information provision node 1501 transmit a multiplex stream multiplexing an AV stream and metadata to the information usage node 1506.
In recent years, a demand has arisen for various kinds of information to be included in metadata, and for metadata to be processed coupled with an AV stream, rather than having metadata simply as ancillary data for an AV stream.
However, in the above-described conventional information processing system, metadata parsing cannot be carried out until all the metadata has been acquired. For example, if metadata begins with <metadata>, metadata parsing cannot be carried out until data </metadata> indicating the end of the metadata arrives.
For this reason, the metadata processing time is closely tied to the AV stream display or processing time, and since an AV stream is processed in accordance with the metadata itself, processing cannot be started until all the metadata has been received. Therefore, in a conventional information processing system, there is a problem in that it is difficult to process an AV stream in small units.
Also, metadata is distributed virtually uniformly in a multiplex stream. As a result, especially when the data quantity of metadata is large, a large AV stream quantity must be read by the time all the metadata is read. Consequently, there are problems relating to inter-node response time delays and increased network traffic.